know-nothing

1. not comparableIgnorant; characterized by foolish denial of facts or beliefs in that which is not true.

   All over the world, know-nothing xenophobes are claiming – without evidence – that climate science is rigged.

   2017 February 20, Paul Mason, “Climate scepticism is a far-right badge of honour – even in sweltering Australia”, in the Guardian

plural know-nothings

1. An ignorant person; one who lacks knowledge.

   Synonyms: ignoramus

plural Know-Nothings

1. UShistoricalgovernmentA member of a secret antiforeigner political organization in the nineteenth-century United States.

   1 more example

   The legacy of the Know-Nothings lived beyond its life as an organization. The seeds of bigotry, fear and hatred bore fruit again in the years after the Civil War.[…] The First World War led to another outbreak of nativism. A new group, adopting the program of the Know-Nothings and the name of the Ku Klux Klan, came into being, denouncing everything its members disliked—Negroes, Catholics, Jews, evolutionists, religious liberals, internationalists, pacifists—in the name of true Americanism and of “Nordic superiority.”

   1964, John F. Kennedy, “Immigration Policy”, in A Nation of Immigrants, Revised and Enlarged edition, Harper & Row, →LCCN, →OCLC, page 71